Drilling fluid methods and composition

ABSTRACT

A method is provided for the prevention of balling of formation cuttings upon the surface of drilling equipment and for lubrication of said equipment used in conjunction with subterranean well operations. An aqueous system is prepared to which is added a composition of a water insoluble polyglycol having a molecular weight of from between about 1,200 and about 10,000, an emulsifying surfactant having a hydrophilic/hydrophobic balance of about 4 or more, and a hydrotrope. An additive for use in the method also is disclosed.

This is a continuation of co-pending application Ser. No. 515,573, filedon Apr. 27, 1990 now U.S. Pat. No. 5,007,489.

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The invention relates to a method for the prevention of balling duringdrilling, completion and workover of subterranean oil and gas wells andto the lubrication of well drilling equipment, as well as to an additivefor such use.

2. DESCRIPTION OF THE PRIOR ART

When drilling, completing or working over subterranean wells in order totap deposits of, for example, oil or gas, and in particular whenutilizing a rotary drilling method comprising a bit to which is attacheda drill stem, the bit will penetrate the formation. The formation iscomposed of both inorganic and organic substances, such as clays andother minerals as well as fossils, peat etc. As the drill bit teethpenetrate the formation, drill chips are generated by the action of thebit. These drill chips are wetted by the drilling fluid which canproduce sticky, plastic fragments. These fragments adhere to the bitsurface and the force and weight of the bit extrudes the water from theplastic fragments forming a compacted mass of the formation onto the bitsurface that interferes with the cutting action of the bit teeth asevidenced by a reduction in penetration rate. Balling also occurs ondrill collars and stabilizers

Bit balling resulting in the compaction and adherence of drill chips tothe face of the cutters and the bit is a primary cause of reduction ofpenetration rate during drilling operations. Bit balling is believed tobe the result of the adhesive forces between shale and the bit surfacewhich become significant when ductile shales deform and are forced intointimate contact with each other and the bit surface.

A liquid adheres to a solid surface if the attraction of the moleculesto the solid surface is greater than their attraction to each other,i.e., the work of adhesion is greater than the work of cohesion. Thiscriterion may be expressed thermodynamically as:

    W.sub.A =F.sub.S +F.sub.L -F.sub.I

Where W_(A) is the work of adhesion; F_(S) is the surface free energy ofthe solid; F_(L) is the surface free energy of the liquid; and F_(I) isthe surface free energy of the newly formed interface. In terms of thisexpression, the work of cohesion, (WC), is In terms of this expression,the work of cohesion, (W_(C)), is equal to 2 x F_(L).

In order for adhesion to occur between the solid surface and a liquid,the work of adhesion must be greater than that of cohesion:

    W.sub.A -W.sub.C =F.sub.S -F.sub.L -F.sub.I

Accordingly, adhesion of the liquid to a solid occurs when the surfacefree energy of the solid surface exceeds that of the liquid andinterface:

    F.sub.S >F.sub.L +F.sub.I

Shales adhere to bits and drill collars if they are forced into intimatecontact by the force and weight of the drill string. The mechanism ofadhesion in this instance is probably hydrogen bonding extending fromthe molecular layers of water absorbed on the surface of the shalesurface to the layer of water adhering to the water-wet steel surface ofthe bit.

In the past, those skilled in the art have particularly relied upon useof oil-based or water-in-oil (invert emulsions) drilling fluids toeliminate or control bit balling although several aqueous based fluidsand additives have been contemplated by those skilled in the art. Theenvironmental problems and costs associated with the use of oil-based orinvert emulsion systems have discouraged and/or prohibited their use onmany wells.

Accordingly, the present invention addresses the problem set forth aboveby providing an aqueous based fluid containing therein a material whichacts as a synthetic oily-like substance to inhibit bit balling uponmetallic surfaces of drilling, completion and workover equipment.

Applicants are aware of the following prior art relating to the generalsubject area of this invention:

    ______________________________________                                        U.S. Pat. No.       PATENTEE                                                  ______________________________________                                        2,241,255           Garrison                                                  2,498,301           Self                                                      3,550,236           Fischer et al                                             2,727,002           Rowe                                                      3,047,494           Browning                                                  3,219,580           Stratton                                                  3,308,068           Jones                                                     3,414,517           Mosier et al                                              3,575,855           Estes                                                     3,762,485           Chesser et al                                             3,979,305           Fischer et al                                             4,040,866           Mondshine                                                 4,063,603           Rayborn                                                   4,064,056           Walker et al                                              4,140,642           Kistler et al                                             4,172,800           Walker                                                    4,212,794           Grodde et al                                              4,289,631           Luxenburg                                                 4,409,108           Carney et al                                              4,425,241           Swanson                                                   4,425,461           Turner et al                                              4,425,462           Turner et al                                              4,425,463           Walker et al                                              4,830,765           Perricone et al                                           ______________________________________                                    

SUMMARY OF THE INVENTION

The present invention incorporates an additive and method for theprevention of balling of formation cuttings upon the surface of drillingequipment, particularly, drill bits, which are used in conjunction withthe drilling, completion or workover of a subterranean well and forimparting lubricity to such drilling equipment and for lubricationpurposes.

The methods comprise the steps of first preparing an aqueous system.Thereafter, to the system is added a composition comprising a non-watersoluble polyglycol having a molecular weight of from between about 1,200and about 10,000, together with an emulsifying surfactant having ahydrophilic/hydrophobic balance of about 4 or more, together with ahydrotrope.

Upon addition of the composition to the aqueous mud system,emulsification is achieved by the shearing action in the mud hopper, ifthe composition is added through the hopper, and the shearing action ofthe surface equipment. Additional shearing will be obtained at the drillbit as the fluid passes through the nozzles of the drill bit which isrotating at high speeds.

The system is introduced into the well for circulation through and outof the well. When it passes through the bit nozzles, the drilling fluidis in contact with the bit surface at which time the emulsion dropletscontact and spread over the bit surface replacing the water filmadhering to the bit surface.

A drilling fluid containing the present invention emulsified thereinwill exhibit a lubricity coefficient lower than that of a similar fluidwithout the composition as determined by the American PetroleumInstitute's "Procedure for Determination of Lubricity Coefficient(Tentative)" 1980.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As contemplated herein, the present invention is intended for use in anaqueous drilling fluid or, as sometimes referred to, an "aqueoussystem". The base for such system may be either fresh water, a brine,sea water or any combinations thereof. The system may also contain otherknown drilling fluid additives, such as bentonite, barite, gums, watersoluble polymers and similar viscosity modifying agents, as well aschemical thinners.

The composition which is utilized in the methods incorporates anon-water soluble polyglycol having a molecular weight of from betweenabout 1,200 and about 10,000. Since an objective in selecting a suitablepolyglycol is that it be non-water soluble, it will be appreciated bythose skilled in the art that molecular weight is a factor in thedetermination of water solubility. Accordingly, it is believed that anypolyglycol having a molecular weight below about 1 200 will have atendency to be water soluble or at least not sufficiently non-watersoluble for satisfactory incorporation into the present invention. Whilean upper molecular weight criteria is not as essential as that for thelower most point of molecular weight, it is believed that a polyglycolin excess of a molecular weight of about 10,000 may not besatisfactorily utilized in the present invention because of difficultyin preparation and handling these more viscous materials.

The non-water soluble component of this invention may be a di-hydroxyalcohol such as a polypropylene glycol or a propoxylated tri-hydroxyalcohol such as polypropylene glycerol. Ethylene oxide propylene oxidecopolymers of di-hydroxy and tri-hydroxy alcohols may also be used.

When incorporated into the present invention, the selected non-watersoluble polyglycol should be added in an amount of about 80% by weightof the total composition utilized in the aqueous system.

The emulsifying surfactant of the present invention concentrates itselfat the surface of the polyglycol droplets forming an interfacial filmaround the droplet, thus lowering the interfacial tension between thepolyglycol droplet and water. Accordingly, the surfactant stabilizes thedroplet, i.e. decreases its need to interact with other droplets(coalesce) in an effort to lower its surface face energy. The surfactantin the interface also promotes the wetting and spreading of thepolyglycol droplet on the bit surface. In the interfacial filmformation, the surfactant orients itself so that the organic "tail"extends into the body of the droplet and the cation associated with itis projected toward the water phase thus producing a droplet whichappears to be positively charged when in contact with the negativelycharged bit and shale surfaces.

The selected emulsifying agent is preferably oil soluble, preferablyanionic and preferably has a hydrophilic/hydrophobic balance of about 4or higher. Those skilled in the art will recognize that thehydrophilic/hydrophobic balance (HLB) may be calculated from thestructural groupings, the formula required depending upon the compound.It is also recognized that HLB values obtained by such calculations arenot absolute and often times differ from the HLB value found byexperimental determination and that HLB values are only a rough guide toemulsification solutions and that HLB values may change when theenvironment in which they are placed changes, i.e. a temperatureincrease.

Preferably, the anionic emulsifying surfactant is oil soluble and is asulfonated petroleum natural acid. Other anionic or nonionic surfactantsmay be selected such as sulfated soybean oil, long chain alcohols,esters of fatty acids and complex amines.

The selected emulsifying surfactant should not cause oil wetting of theweighting agent and solids in the aqueous system nor should the amountthereof produce a foam. The amount of the selected emulsifyingsurfactant normally will be surprisingly small, on the order of about10% of the total weight of the composition used in the aqueous system.It has been found that incorporation of the selected emulsifyingsurfactant for use in the present invention at this level will provide acomparably tight emulsion, resulting in the formation of stable dropletsof oil-like substance for adherence to the metallic surface of the drillbits, and other drilling equipment.

The hydrotrope of the present invention is incorporated to make thesurfactant and polyglycol of composition of the present invention morecompatible and to make the composition more compatible with the aqueousphase of the drilling fluid. In practicing the present invention, anywater soluble salt of a sulfonated xylene may be utilized as theselected hydrotrope. Preferably, sodium xylene sulfonate may beutilized, but other water soluble salts selected from the classconsisting of water soluble salts of sulfonated xylene, cumene andtoluene may be selected as the hydrotrope for use in the presentinvention.

The composition of the present invention when utilized in the methodsdoes not form a satisfactory emulsion without shearing. Such shearingmay be created by application of surface mixing equipment used indrilling mud compounding when prepared in, for example, a mud pit at thewell site. Alternatively, the composition may be placed into acirculated aqueous system introduced into the subterranean well and theshearing action of the fluids by the pumps and jet nozzles will form astable polypropylene glycol in water emulsion of the composition in theaqueous system. The small but stable polypropylene glycol droplets thusformed will adhere to the drill bit or other metallic surface of thedrilling equipment to provide a non-water wetting interface between suchsurface and the water-wet shale fragments in the aqueous system toprevent balling.

As the drilling fluid containing the aqueous system and the emulsifiedcomposition of the present invention is circulated within thesubterranean well, it will come in contact with the surfaces of thedrill bit. The emulsified droplets of the composition will adhere andspread over the bit surface causing it to be polyglycol wet thusresulting in an interruption of the water-to-water bonding which occursbetween the water-wet bit surface and the water-wet shale which in turneliminates the tendency for bit balling. Such contact will also impartlubricity to the surface of such equipment, reducing for exampleproblems of differential sticking, torque and the like.

As an alternative to preparation of the emulsion of the composition ofthe present invention as described above, such emulsion may be preparedin situ. For example, the polyglycol may be added to the aqueous systemwhich has therein satisfactory emulsifying surfactants and which may ormay not contain a hydrotrope. Thus, the in situ preparation of theemulsion is contemplated.

A laboratory method has been established for testing and examining theadhesive and cohesive forces between shale to metal and shale to shalewhich are involved in the bit balling phenomenon. In such method, aCarver press is used to form a shale disc in a steel mold under aconfining pressure onto a metal plate having a surface roughness (RMS)of 300. The force, in pounds, required to shear the shale disc from thesurface of the steel plate is measured with a MTS instrument. In actualtests, the freshly cleaned water-wet metal plate is coated with a thinfilm of the sample fluid before the mold and shale are placed on it. Apressure of 2,500 psi is applied to the shale for ten minutes before theadherence value is determined. In using this testing procedure, theadherence value, in pounds, for a water-wet plate was found to be175-225, whereas the adherence value for an oil-wet plate was found tobe 0. According to this test, the closer the adherence value preventingbit balling.

A drilling fluid in which the composition of the present invention hasbeen emulsified has been found to have excellent lubricitycharacteristics. For the purpose of determining lubricity, we haveutilized in our testing the "Procedure for Determination of LubricityCoefficient" (Tentative), a standardized testing procedure published bythe American Petroleum Institute, (1980) as follows:

1. Calibration of Instrument

a. Prepare a calibration curve for conversion of ammeter reading tolubricity coefficient by using a Prony brake and procedure provided withthe instrument.

b. Recalibrate if the drive motor is altered or replaced.

2. Standardization of Test Ring and Block

a. Wash the test ring and block with water and a household cleanser.Rinse thoroughly with water.

b. Place the test ring on the tapered shoulder at the bottom of theshaft and secure with the lock nut.

c. Place the test block in the holder, concave side face out, and alignwith the test ring.

d. Fill the sample container with water (approximately 300 cm³) andposition it so that the test surfaces are covered.

e. Attach a rheostat in series with the instrument and turn on the drivemotor. Adjust the rheostat until the tachometer on the drive shaft reads60 rpm.

f. Apply 150 in.-lb load with the torque arm. Maintain speed at 60 rpm.

g. Observe meter reading in amperes and refer to the calibration chartfor the lubricity coefficient. Run for several minutes or until thereading stabilizes. The lubricity coefficient for water should bebetween 0.33 and 0.36. If it is not in this range, the ring and blocksurfaces should be reconditioned using one of the following methods:

(1) Continue to operate the instrument at a constant load of 150 in.-lbwith water in contact with the test surfaces. The ammeter reading shouldslowly approach the test range of 33 to 36 and then remain steady.

(2) Operate the instrument using a slurry of about 25 lb per bbl ofbentonite in fresh water and a load of 150 in.-lb. Repeat step (1).

(3) Place a grinding compound on the contact surfaces and operate theinstrument at a load of 150 in.-lb. Repeat Step (1).

3. Determination of Mud Lubricity Coefficient

a. Assemble the instrument and standardize the test ring and block togive a 0.33 to 0.36 lubricity coefficient for water.

b. Stir the mud sample ten minutes on a Multimixer prior to testing.

c. Place the mud sample in the container and position to cover the ringand block.

d. Start the motor and adjust the rheostat to give 60 rpm with a load of150 in.-lb.

e. Operate the instrument until the ammeter reading stabilizes.

f. Use the calibration curve to convert the ammeter reading to lubricitycoefficient.

EXAMPLE I

Using the procedure outlined above, several compositions in accordancewith the present invention were prepared using polypropylene glycolshaving selected molecular weights of 1000 and 2000. The nonionicemulsifying surfactant was Neodol 25-7, which is a C₁₂ -C₁₅ nonioniclinear primary alcohol ethoxylate made by Shell Chemical Co. In sometests, the selected anionic emulsifying surfactant was Drillaid 403which is a complex amine sulfonate prepared from about 4 parts of a halfammonium, half isopropylamine salt of the sulfosuccinic acid ester ofthe oleic acid amid of isopropanol amine and about 1 part of theisopropylamine salt of dodecyl benzene sulfonic acid, made in accordancewith U.S. Pat. No. 3,472,768. Another nonionic emulsifying surfactantwas BRIJ 72 which is a polyoxyethylene stearyl ether, manufactured byICI Americas Inc. Adherence force, in pounds, was determined, as setforth above. The results of the tests indicated that when the non-watersoluble polyglycol having a molecular weight above about 1200 wasutilized an unstable emulsion was formed, yet a decrease in adherencevalue was obtained. However, when the polyglycol was emulsified inaccordance with the present invention, adherence values were furtherdecreased. The results 1 of this test are set forth in Table 1, below:

                  TABLE 1                                                         ______________________________________                                        ADHERENCE VALUES OF POLYPROPYLENE                                             GLYCOL IN WATER EMULSIONS                                                     Polypropylene Glycol                                                                       Surfactant  Water    Adherence                                   % (Wt.)                                                                              Mol. Wt.  % (Wt.)  Type % (Wt.)                                                                              Value lbs.                              ______________________________________                                        0                0        --   100    162,229                                 2.5    1000      0        --   97.5   44                                      2.5    2000      0        --   97.5   100                                     2.4    1000      0.3      A    97.3   60,18                                   2.9    2000      1.4      B    95.7    0,16                                   2.9    1000      1.4      B    95.7   9,0                                     2.4    2000      0.9      C    96.7    0,33                                   ______________________________________                                         A = ethoxylated linear primary alcohol  nonionic (Neodol 257, Shell           Chemical Co.)                                                                 B = complex amine salts  anionic                                              C = ethyoxylated alcohol ether  nonionic (BRLJ 72, ICI Americas Inc.)    

EXAMPLE II

Tests were conducted and results were evaluated as in Example I, above,and the selected non-water soluble polyglycerol was propylene glycerol.In some of the tests, combinations of the selected glycerol at twodifferent molecular weights were tested. The results are set forth inTable II, below:

                  TABLE 2                                                         ______________________________________                                        ADHERENCE VALUES OF POLYPROPYLENE                                             GLYCOL IN WATER EMULSIONS                                                     Polypropylene                                                                 Glycerol     Surfactant  Water    Adherence                                   % (Wt.)                                                                              Mol. Wt.  % (Wt)   Type % (Wt) Value lbs.                              ______________________________________                                        0      --        0        --   100    162,229                                 2.5    2000      --            97.5   55                                      2.5    3000      0        --   97.5   69                                      2.5    7500      0        --   97.5   27                                      2.4    2000      0.9      A    96.7   66                                      2.4    3000      0.9      A    96.7   20,10                                   2.4    7500      0.9      A    96.7   0,6,25                                  2.9    2000      1.4      B    95.7    0                                      2.9    3000      1.4      B    95.7   13                                      1.4    7500      1.4      B    95.7    0                                      1.4    3000                                                                   2.1    7500      1.4      B    95.7    0                                      0.7    3000                                                                   0.7    7500      1.4      B    95.7    0                                      2.1    3000                                                                   ______________________________________                                         A = ethoxylated linear primary alcohol  nonionic (Neodol 257, Shell           Chemical Co.)                                                                 B = complex amine salt  anionic                                          

EXAMPLE III

The method of the present invention was demonstrated in actual fieldapplication by preparing an aqueous system whose primary constituentswere bentonite, a copolymer of 2-acrylamido-2-methyl propane sulfonicacid (AMPS) /acrylamide (AM) and barite to which was added a compositionwith a non-water soluble di-hydroxy alcohol being polypropylene glycolin an amount of about 80% by weight of the total compositionformulation, together with Petrosul H-50 as the selected anionicsurfactant in an amount of about 10% by weight of the total composition.The hydrotrope was sodium xylene sulfonate in an amount of about 10% byweight of the entire composition formulation. The composition was addedto a water based drilling fluid at the mud plant and/or on location.Emulsification was achieved by shearing with the surface mixingequipment.

The system was introduced into the well for circulation through and outof the well and the composition contacted the selected drill bit toprovide a polypropylene glycol film between the drill bit and thedrilled shale chips.

The ability to prevent bit balling in these actual field applications isdemonstrated by the average rate of penetration calculated in drilledfeet per hour, compared with the through similar formations at the sameapproximate depths but with oil base, (invert emulsion) and water baseddrilling fluids. The well drilled with a fluid containing thecomposition of the present process was identified as well "A". Theaverage rate of penetration in this well was 23 feet per hour whichcompared quite favorably to the average rate of penetration of 21.6 feetper hour for the seven (7) wells drilled with the oil based fluid. Theaverage rate of penetration ("ROP") for wells "C", "D" and "I" were32.6% to 2.2% higher than that of well "A" while the average ROP forwells "D", "F", "G" and "H" were 42.2% to 3.0% lower. Well "B" wasdrilled using a lignosulfonate/potassium hydroxide water based drillingfluid, resulting in an average rate of penetration of 12.4 feet perhour, 46.1% less than the average ROP of well "A". For well "J" whichwas drilled with a polymer water based drilling fluid, the average ROPwas 20.2 feet per hour or 12.2% less than that of well "A". The resultsof this test are set forth in Table 3:

                  TABLE 3                                                         ______________________________________                                                                       Drill-                                                                              Avg.  %                                  Well           Bit       Feet  ing   ROP,  Chg.                               No.  Mud Type  Size   No.  Drilled                                                                             Time  ft/hr ROP                              ______________________________________                                        A    Water-base                                                                              83/4"  3    2,697 117.5 23.0  --                               B    Water-    81/2"  5    2,297 185.5 12.4  -46.1                                 base*                                                                    C    Oil-base  83/4"  2    2,305 90    25.6  +11.3                            D    Oil-base  61/8"  4    2,550 192   13.3  -42.2                            E    Oil-base  83/4"  1    1,890 62    30.5  +32.6                            F    Oil-base  81/2"  3    2,773 167   16.6  -27.8                            G    Oil-base  83/4"  3    2,400 125.5 19.1  -17.0                            H    Oil-base  81/2"  4    2,501 112   22.3   -3.0                            I    Oil-base  83/4"  3    4,855 206.5 23.5   +2.2                            J    Polymer** 81/2"  3    2,983 147.5 20.2  -12.2                            ______________________________________                                         *Lignosulfonate/KOH fluid                                                     **Hydrolyzed polyacrylamide in water                                     

EXAMPLE IV

The process of the present invention was demonstrated in a second fieldapplication by preparing an aqueous system as described in Example III.Well "A" was drilled with a fluid containing the composition of thepresent process. The average ROP for it was 30.3 feet per hour and itwas drilled in 255 hours using only 3 bits. Wells "B" and "C" weredrilled with lignosulfonate water based drilling fluids. The average ROPfor well "B" was 22.8 feet per hour and 11 bits were required while forwell "C" the average ROP was 19.2 and 12 bits were required. Thedecrease in the number of bits used when drilling with a fluidcontaining the composition of the present process (Well "A") isindicative of the lubricating qualities of the present composition. Theresults of this test are set forth in Table 4:

                  TABLE 4                                                         ______________________________________                                                                        Drill-                                                                        ing        %                                  Well           Bit        Feet  Time/ Avg. Chg.                               No.  Mud Type  Size    No.  Drilled                                                                             Hrs.  ROP  ROP                              ______________________________________                                        A    Water-base                                                                              9.875"   3   7,710 255   30.3 --                               B    Water-base                                                                              9.875"  11   8,545 377   22.7 -25.1                            C    Water-base                                                                              9.875"  12   7,048 366.5 19.2 -34.7                            ______________________________________                                    

The invention composition when used as described above will perform as alubricant in the mud system. The polyglycol wet surfaces of the drillingassembly and bit glide more freely through the fluid because of thedecreased attraction between the polyglycol-wet assembly and bit and theaqueous fluid.

EXAMPLE V

To demonstrate the lubricating properties of the present invention alaboratory mud was prepared consisting of 10 lb/bbl sodium bentonite; 1lb/bbl AMPS-AM copolymer; 1 lb/bbl CMC; 165.4 1b/bbl barite; and 21.9lb/bbl simulated drill solids. Using the method previously described,the lubricity coefficient of the mud before and after varying amounts ofthe composition were added to the base mud.

As shown in Table 5, the addition of 2.5% by volume of the presentcomposition reduced the lubricity coefficient by 58% and the addition of4.5% by volume reduced the lubricity coefficient by 81%.

                  TABLE 5                                                         ______________________________________                                        Lubricity Coefficient                                                         Polypropylene Composition                                                                       Lubricity Coefficient                                       ______________________________________                                        0 (base mud)      0.31                                                        2.5               0.13                                                        3.5               0.05                                                        4.5               0.06                                                        5.5               0.06                                                        ______________________________________                                    

EXAMPLE VI

Tests were performed, as above, to determine the lubricity coefficientof a base mud having present therein polypropylene glycols of varyingmolecular weights, with the polypropylene glycols being added to thebase mud composition. The results of this test are set forth in Table 6which indicates that each of the molecular weight materials, within thescope of the claims of this invention, decreased the lubricitycoefficient significantly.

                  TABLE 6                                                         ______________________________________                                                     Lubricity                                                                     Coefficient                                                                           % Decrease                                               ______________________________________                                        Base Mud       0.27                                                           +4% 1200 PPG   0.21      22.2                                                 +4% 2000 PPG   0.20*     25.9                                                 +4% 4000 PPG   0.20*     25.9                                                 +4% 5700 PPG   0.23*     14.8                                                 ______________________________________                                         Base Mud Composition                                                          25 lb/bbl gelling agent                                                       0.6 lb/bbl NaOH                                                               1.0 lb/bbl sodium lignosulfonate                                              29.0 lb/bbl barite                                                            *Emulsion broke during test.                                                  Number before PPG is the average molecular weight.                       

EXAMPLE VII

The present example was performed incorporating polypropylene glycoladditives including an identified surfactant. The results of this testare set for in Table 7, below:

                  TABLE 7                                                         ______________________________________                                        Effect of Polypropylene Glycol-Surfactant Mixtures                            On Lubricity Coefficient of a Drilling Fluid                                                  Lubricity                                                                     Coefficient                                                                            % Decrease                                           ______________________________________                                        Base Mud          0.27                                                        +4% 1200 PPG-Span 20                                                                            0.05       81.5                                             +4% 1200 PPG-Tween 85                                                                           0.10       63.0                                             +4% 2000 PPG-Brij 92                                                                            0.12       55.5                                             +4% 4000 PPG-Neodol 25-3                                                                         0.19*     25.9                                             +4% 4000 PPG-Petrosul H-50                                                                      0.03       88.9                                             +4% 5700 PPG-Petrosul H-50                                                                      0.03       88.9                                             ______________________________________                                         *Emulsion broke during testing.                                               Number before PPG is the average molecular weight.                            Base Mud Composition                                                          25 lb/bbl gelling agent                                                       0.06 lb/bbl NaOH                                                              1.0 lb/bbl sodium lignosulfonate                                              29.0 lb/bbl barite                                                            1. The Polypropylene glycolsurfactant additions consists of 90% PPG and       10% surfactant.                                                               2. Surfactants:                                                               Span 20 . . . sorbitan monolaurate, nonionic, HLB 8.6                         Brij 92 . . . polyoxyethylene olyel ether, nonionic, HLB 4.9                  Neodol 253 . . . linear primary alcohol ethoxylate, nonionic, HLB 7.9         Petrosul H50 . . . sodium petroleum sulfonate, anionic,                       Tween 85 . . . sorbitan trioleate, nonionic, HLB 11.0                    

EXAMPLE VIII

The present test was performed to determine the lubricity coefficient ofvarying molecular weight polypropylene glycerols which were added tobase mud compositions. In each instance, the materials decreased thelubricity coefficient. The results of this test are set for in Table 8,below:

                  TABLE 8                                                         ______________________________________                                                     Lubricity                                                                     Coefficient                                                                           % Decrease                                               ______________________________________                                        Base Mud       0.27                                                           +4% 750 PG     0.21*     22.2                                                 +4% 3000 PG    0.20*     25.9                                                 +4% 7500 PG    0.20*     25.9                                                 ______________________________________                                         Base Mud Compositon                                                           25 lb/bbl gelling agent                                                       0.06 lb/bbl NaOH                                                              1.0 lb/bbl sodium lignosulfonate                                              29.0 lb/bbl barite                                                            *Emulsion broke during testing.                                               Number before PG (polypropylene glycerol) is the average molecular weight                                                                              

EXAMPLE IX

The present example demonstrates the effect of polypropyleneglycerol-surfactant materials on lubricity coefficient. The results ofthis test are set for in Table 9, below:

                  TABLE 9                                                         ______________________________________                                                        Lubricity                                                                     Coefficient                                                                            % Decrease                                           ______________________________________                                        Base Mud          0.27                                                        +4% 750 PG-Tween 85                                                                              0.17*     37.0                                             +4% 750 PG-Span 20                                                                               0.02*     92.6                                             +4% 3000 PG-Actrasol MY-75                                                                       0.02**    92.6                                             +4% 3000 PG-Brij 92                                                                             0.10       63.0                                             +4% 7500 PG-Petrosul H-50                                                                       0.03       88.9                                             +4% 7500 PG-Span 20                                                                             0.03       88.9                                             ______________________________________                                         *Emulsion very foamy.                                                         **Emulsion partially broke during testing.                                    Notes:                                                                        1. The polypropylene glycerolsurfactant addition consisted of 90% PG and      10% surfactant.                                                               2. Surfactants:                                                               Tween 85 . . . sorbitan trioleate, nonionic, HLB 11.0                         Span 20 . . . sorbitan monolaurate, nonionic, HLB 8.6                         Actrasol MY75 . . . sulfated soybean oil, anionic                             Brij 92 . . . polyoxyethylene oleyl ether, nonionic, HLB 4.9                  Petrosul H50 . . . sodium petroleum sulfonate, anionic                        3. Number before PG indicates average molecular weight.                  

EXAMPLE X

The present example demonstrates the ability of the composition of thepresent invention, including a surfactant, a hydrotrope, and apolyglycol to decrease the lubricity coefficient of a drilling fluid.The results of this test are set forth in Table 10, below:

                  TABLE 10                                                        ______________________________________                                        Effect of Hydrotrope on Lubricity Coefficient                                                   Lubricity                                                                     Coefficient                                                                           % Decrease                                          ______________________________________                                        Base Mud            0.25                                                      +4% 1200 PPG-Span 20-SXS                                                                          0.03      88                                              +4% 2000 PPG-Brij 92-SXS                                                                          0.12      52                                              +4% 4000 PPG-Actrasol My-75-SCS                                                                   0.03      88                                              +4% 5700 PPG-Tween 85-SCS                                                                          0.18*    28                                              +4% 4000 PPG-Tween 85-SXS                                                                          0.23*     8                                              +4% 750 PG-Span 20-SCS                                                                             0.04**   84                                              +4% 3000 PG-Petrosul H-50-SCS                                                                     0.03      88                                              +4% 7500 PG-Actrasol My-75-SXS                                                                    0.02      92                                              +4% 7500 PG-Petrosul H-50-SXS                                                                     0.02      92                                              ______________________________________                                        *Mud flocculated                                                              **Foamed severely                                                             Notes:                                                                        1. PPG = polypropylene glycol, number before indicates average                molecular weight                                                              2. PG = polypropylene glycerol, number before indicates                       average molecular weight                                                      3. Surfactants                                                                Span 20 . . . sorbitan monolaurate, nonionic HLB 8.6                          Brij 92 . . . polyoxyethylene oleyl ether, nonionic HLB 4.9                   Actrasol My-75 . . . sulfated soybean oil, anionic                            Tween 85 . . . sorbitan trioleate, nonionic HLB 11                            Petrosul H-50 . . . sodium petroleum sulfonate, anionic                       Mud Composition                                                                            lb/bbl                                                           gelling agent                                                                              25                                                               sodium lignosulfonate                                                                       1                                                               Barite       29                                                               NaOH           0.06                                                       

In accordance with the present invention, it will be appreciated thatthe surfactant may, or may not, be included with the compositionintroduced originally into the well. The selected polyglycol may,accordingly, be introduced either with the surfactant, or before, orsubsequent to the introduction of the surfactant.

It will also be appreciated that the use of a hydrotrope may, or may notbe, particularly desirable in view of the working parameters of thedrilling fluid and the selected and particular composition at hand.

Although the invention has been described in terms of specifiedembodiments which are set forth in detail, it should be understood thatthis is by illustration only and that the invention is not necessarilylimited thereto, since alternative techniques will become apparent tothose skilled in the art in view of the disclosure. Accordingly,modifications are contemplated which can be made without departing fromthe spirit of the described invention.

What is claimed and desired to be secured by Letters Patent is:
 1. Amethod for the prevention of balling of formation cuttings upon thesurface of drilling equipment used in conjunction with the drilling,completion or workover of a subterranean well, comprising the stepsof:(1) preparing an aqueous system; (2) adding to said system anon-water soluble polyglycol having a molecular weight of from betweenabout 1,200 and about 10,000; (3) introducing the system containing saidpolyglycol into the well for circulation through and out of said well;and (4) contacting the surface of said drilling equipment with saidpolyglycol to provide a non-aqueous interface between the equipmentsurface and the aqueous system.
 2. The method of claim 1 wherein thenon-water soluble polyglycol is polypropylene glycol.
 3. The method ofclaim 1 wherein the non-water soluble polyglycol is polypropyleneglycerol.
 4. The method of claim 1 wherein the non-water solublepolyglycol is derived from a di- or tri- hydroxy alcohol.
 5. In asubterranean well into which is inserted a metallic conduit to the endof which is affixed a drill bit, the method of lubricating the exteriorof said conduit and said drill bit to abate differential sticking, andthe like, comprising the steps of:(1) circulating into said well adrilling fluid having present therein a non-water soluble polyglycolhaving a molecular weight of from between about 1,200 and about 10,000;and (2) contacting the exterior of said conduit and said drill bit withan effective lubricating amount of said polyglycol.
 6. The method ofclaim 5 wherein the non-water soluble polyglycol is polypropyleneglycol.
 7. The method of claim 5 wherein the non-water solublepolyglycol is polypropylene glycerol.
 8. The method of claim 5 whereinthe non-water soluble polyglycol is derived from a di- or tri- hydroxylalcohol.